The present invention relates to diamond blades for use in eye surgery and a novel method for performing a radial keratotomy/keratorefractive (RK) surgical procedure. More particularly, the invention is directed to a novel blade design and method which allow corneal incisions in an RK procedure to be made more effectively and efficiently.
Radial keratotomy RK is a surgical procedure intended to correct myopia (near sightedness). During the procedure, the surgeon uses a diamond-bladed knife to make 4 or more spoke-like radial cuts of a controlled depth in the paracentral and peripheral cornea to produce a flattening effect on the cornea. Exact incisions and a precise depth of cut are important so that the correction of curvature of the cornea is not too great or not great enough.
The knife blade is held by a handle which normally includes a pair of footplates positioned on either side of the blade, which are designed to slide along the outer surface of the cornea. The location of the footplates relative to the tip of the blade can be adjusted by a micrometer setting to control the depth of cut.
Since an RK procedure involves cutting the cornea of a human eye, great care must be taken to make sure that the cuts are precise and at the depth necessary to provide for the indicated correction. Consistent results are difficult to achieve. A problem which has been known to occur is an under correction of the myopia through cuts which are not as deep or precise as indicated. Cuts are normally made conservatively because the knife is extremely sharp and many surgeons tend to be over-cautious when the knife is close to the optical zone.
Several RK surgical procedures are popular in the United States. One is known as the American method, where an initial wound is formed by plunging the knife at the edge of the optical zone marked on the cornea, and moving the knife away from the optical zone. Another method, known as the Russian method, involves making the initial wound at the limbus or outer portion of the cornea and cutting toward the optical zone, ending at the edge of the optical zone marked on the cornea.
Even though the American style is considered to be more comfortable to use since the knife is plunged initially at the edge of the optical zone so the possibility of impinging on the optical zone at the end of the cut is minimized, the cut is not squared off at the optical zone because of the normal travel path of the knife during initial plunge. Also, because of vector forces acting on the knife, a uniform cut at the proper depth is difficult to make along the entire incision without excessive pressure being exerted, through the footplates of the knife on the outer surface of the cornea.
While the Russian method tends to result in cuts that are more squared off toward the edge of the optical zone and requires less cutting pressure, many surgeons tend to be more tentative at the end of the cut in order to avoid impinging on the optical zone. This tends to result in an incision which does not extend up to the edge of the optical zone.
Another problem that occasionally arises is that the knife blade is not properly set during an incision. It is difficult to retrace the cut at the proper setting without straying from the exact path of the initial cut.
It would be advantageous to the surgeon to combine the safety of the American style with the efficiency and more predictable results of the Russian style by the squaring off of incisions at the edge of the optical zone. It would also be advantageous to provide a surgical knife which can be used to square off incisions after an initial cut is made without having to worry about cutting new tissue outside of the initial incision.